Signal identification system

ABSTRACT

A system is disclosed for reducing analog signal patterns or sequences to concise digital representations for identification, as to recognize an audio signal, for example, manifesting a musical recording. In the system, audio (analog) signals are sampled for dissection into a plurality of values which are accumulated over a sampling interval to provide an aggregate value. Preliminary to such a sampling operation, the signal of interest may be frequency dissected into a plurality of individual signals which are sampled then summarized or totalled. The aggregate total numerical values are reduced to a representative form by encoding them in accordance with their relative significance. Operation over repeated sampling intervals affords an expanded basis for indentification and recognition.

United States Patent 1191 Goldman 14 1 May 7,1974

[ SIGNAL IDENTIFICATION SYSTEM [76] Inventor: Robert N. Goldman, 16661Akron St., Pacific Palisades, Calif. 90272 [22] Filed: Apr. 5, 1972 [21]Appl. No.: 241,391

Related U.S. Application Data [63] Continuation of Ser. No. 46,352, June15, 1970,

340/347 AD; 235/616 A; 17/1 SA, 1 SB Primary Examiner-Thomas A. RobinsonAttorney, Agent, or FirmNilsson, Robbins & Berliner [5 7 ABSTRACT Asystem is disclosed for reducing analog signal patterns or sequences toconcise digital representations for identification, as to recognize anaudio signal, for example, manifesting a musical recording. In thesystem, audio (analog) signals are sampled for dissection into aplurality of values which are accumulated over a sampling interval toprovide an aggregate value. Preliminary to such a sampling operation,the signal of interest may be frequency dissected into a plurality ofindividual signals which are sampled then summarized or totalled. Theaggregate total numerical values are [56] References Cited reduced to arepresentative form by encoding them in UNITED STATES PATENTS accordancewith their relative significance. Operation 3,466,39 9/1969 French 179/1S over repeated sampling intervals affords an expanded 3,037,077 5/1962Williams et al. 179/1 SB basis f i d tifi i and recognition. 3,445,8405/1969 Carlstead 340/347 3,398,241 8/1968 Lee 179/1 SA 7 Claims, 7Drawing Figures 46 56 S/QMPL/A/G 0/ Acct/Momma c/RCU/T CLEAR g 36 /38 4942 48 72 r58 F/MQLOG QCCUMUL/QTOR 22 S/GMQL C/RCU/T CL 577R l l ,/44 l6O S/QMPL/A/G QCCUMULQTOR g C/RCU/T tree/7R 60 J 1 CLOCK 77 73 DEL/WICOUNTER i 7@ Q6974 TEST GATE D/6/ TFH COD/M6 f74 68 U GATE & e

CROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation of application Ser. No. 46,352, filed June 15, 1970 and nowabandoned.

BACKGROUND AND SUMMARY OF THE INVENTION The desire sometimes occurs torecognize, or identify analog signal patterns, as for example, aninterval of an audio signal. As a specific example, it may be desirableto monitor a radio broadcasting station with the objective of providinginformation on the individual musical selections that are broadcast bythe station during a particular logging interval. That is, rather thanto manually record a broacast log as a basis for royalty payments, andso on, a signal-recognition system could develop a compilation of thebroadcast material with improved economy and accuracy.

It has been previously proposed to monitor a broadcast station byproviding a code on each and every recording that is to be identified ifand when it is broadcasted, then detecting the occurrence of the code inthe broadcast radio signal, as a basis for compiling a broadcast log.Although such an arrangement affords certain advantages, its commercialimplementation has appeared to be exceedingly difficult. Specifically, agreat problem is presented in obtaining and maintaining recorded codeson all the recordings of interest which may be containedin the broadcastmaterial from a station. Additionally, broadcasting codes and so on maypresent difficulties with regulatory authorities and furthermore,substantial difficulty arises with regard to the problem of selectivelysensing the coded information, i.e., discriminating in favor of codesignals and against the other content of a broadcast signal.Consequently, systems of this type have not generally been consideredfor serious commercial use.

In any signal-recognition system, for use to identify a particularsequence or pattern that is contained in a substantially-continuous;signal, one of the problems is related to timing. That is, if arecognition system were provided with synchronizing signals as well asthe signal of interest, the problem would be substantially simplified.However, in the exemplary application considered above, i.e., monitoringthe signal from a commercial radio broadcasting station, synchronizinginformation is not present to indicate intervals of concern.Accordingly, a system for such an operation must have the capability tomonitor a substantially-continuous signal,

e.g., the audio content of a standard radio broadcast signal, andrecognize the occurrence of specific sequences or patterns, e.g.,recordings, contained within the broadcast signal, without the benefitof any timing or synchronizing signals from the radio station.

In general, the system hereof functions to accomplish the objectivesconsidered above by developing digital numerical representations thatare indicative of sequences of the signal under consideration. Suchnumerical representations are developed by dissecting the analog signalof interest (sampling, filtering, and encoding). The system may beimplemented to search for a coincidence with any of manysimilarly-developed numerical representations which are established instaggered relationship to each other.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which constitute apart of this specification, exemplary embodiments demonstrating variousobjectives and features hereof are set forth as follows:

FIG. 1 is a block diagram of an exemplary system incorporating thestructure of the present invention.

FIGS. 2 and 3 are sets of waveforms illustrative of the operation of thepresent invention;

FIG. 4 is a block diagram of one embodiment constructed in accordancewith the present invention;

FIG. 5 is a block diagram of a portion of the system of FIG. 4;

FIG. 6 is a diagram illustrating the operation of the system of FIG. 4;and

FIG. 7 is a block diagram of another embodiment incorporating theprinciples of the present invention.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS Referring initially to FIG.1, a system is generally depicted for monitoring the broadcast contentof a plurality of radio stations by using multiplexing techniques.Specifically, a plurality of radio receivers R1 through RN arerepresented, each of which is tuned to receive a selected-station radiobroadcast signal. Of course, the number of individual radio receiversprovided depends upon the number of stations desired to be monitored andthe extent of multiplexing. 7

Each of the radio receivers R1 through RN provides a detected audiosignalto a signal pattern recognition system 12, which reduces eachof'the received audio signals (as described below) to a series ofdigital representations. The operation is similar with regard to each ofthe received audio signals, the analysis of each resulting in separateand distinct data. Accordingly, one signal may be considered asrepresentative of all for purposes of explanation. Therefore, assume,for example, that a particular recording (musical selection) istransmitted by the station monitored by the receiver R1. That audiosignal (representing a musical selection) is reduced to a sequence ofdigital signal representations that are passed through a cable 14 to astorage unit 16. Specifically, for example, (each two seconds) of theaudio signal under observation might be analyzed or dissected to provideone set of digital representations, e.g., a seven-digit decimal numeral.Accordingly, a particular recording can be productive of a series ofnumerical values, each being developed from a brief interval of therecording.

A pattern of such numerals may thus identify a particular sequence of anaudio signal. Consequently, as disclosed in detail below, such data maybe cataloged in advance, for comparative analysis so as to recognizethat a specific recording has been broadcast. Thus, the significantconsideration is that, a sequence of an analog signal extending over atime interval and with almost infinite possibilities, is reduced to aconcentrated set of digital values. Furthermore, the digital values maybe repeatedly duplicated and consequently truly identify the analogsequence.

It is to be appreciated that the digital numerals as set forth above(developed from a specific recording) may vary depending upon theprecise instant of the starting interval during which the audio signalis analyzed or dissected. That is, if the first two seconds were at thebe performed, in accordance with somewhat conventional techniques toindicate identification.

In an exemplary system hereof, a catalog of digital numerals for recordsof concern is registered by a template tape unit 18 and signalsrepresentative of the digital numerals are supplied to a comparison unit20 as indicated. The comparison unit 20 also receives thesignal-represented numerals from the storage unit 16, ei-

ther directly or indirectly as indicated by' a dashed line 22. Thecomparison unit manifests the coincidence of similar sets of numeralscontained in the data'from the template tape unit 18 and that from thestorage'unit 16. Upon the occurrence of a coincidence; a particularrecordingis designated'whereupon a signal identifying that recording ispassed through acable 24 to a recording'unit '26- as the basis for a logof the broadcast moni- 'tored by the radio receiver Rl.'"-

The system as disclosed in FIG. 1 is indicated to operate incooperation-with a plurality of radiore'ceivers R1 through RN. Assuggested above, although description has been directed to a singleaudio signal, it is to be appreciated that by the use of well-knowntime-sharing and multiplex techniques, a plurality of broadcast stationscan be concurrently monitored by means well knwon in the art. Inthatregard, the signal pattern system 12 comprises the key element of thecombination.

in view of the above preliminary description of the present system,reference will now be made to FIG. 2 (and subsequentlytoFlG. 3) for ananalytical consideration of the techniques for developing sets ofnumerals from sequences of an analog or audio signal. Specifically, thecurve of FIG. 2(a) represents an audio signal that is to be defined overa relatively-short interval of time, e.g., two seconds; The signalrepresented in the curve of FIG. 2(a) varies in amplitude about areference level indicated by a line 30. As an initial step, the signalas represented may be rectified with reference to the reference level toprovide a single polarity signal as represented by the curve 32 of FIG.2(b).

One of the definitive characteristics of the curve 32 is the total areathereunder. That is, an indication of the total area under the curve 32during the interval T is an identifying characteristic of the curve. Onetechnique for developing a representative value for the area under thecurve is to sample the signal represented by the curve 32 at regularintervals and accumulate the aggregate value of the individual samples.Such an operation may be related to the mathematical process ofintegration. That is, the curve 32 may be dissected into a plurality ofsample amplitude values as indicated by the lines 34. By'accumulatingsuch values represented by the lines 34 over the interval T, anaggregate value is developed which is related to the area defined underthe curve 32. i

Although the area under a curve is an identifying characteristic of acurve, it is rather ambiguous in that many totally-different curves willdefine similar areas. Consequently, further identification of a 7signal, as represented by a curve, is generally necessary in a practicalsignal-identification system.

Prior to dissecting a signal by sampling, (as considered-above) thecurve may be dissected on a frequency basis. For example, anaudio signaloccurring during a time interval T might be filtered to provide threecomponent frequency signals which may'zthen be" rectified to forms asrepresented by the curves shownv in FIGS.

3(a), 3(b) and 3(0). By frequency dissecting an analog signal, itsunique characteristics are moreeffectively defined by'three separatesignals FlG..3) which then may be individually sampled to develop threeaggregate numerical values. Such values are considerably more definitiveof the signal than the prior single-value asconsideredabove withreference to FIG. 2. Thus, if

each of the signals represented by the curves of FIGS. 3(a), .3 (b) and3(0) are individually sampled 'overan interval T and the samples foreach signal are accumulated, three values of considerable significanceand def inition will result. I ln aceordance'herewith, the aggregatenumerical values developed'by the method considered above areeffectively reduced by encoding them on the. basis of theirrelativesignificance.v That is, an identifying code value is assignedtothe analog signal, dependent upon the relative magnitudes of a pluralityof numerical values developed, which'code affords a rather conciseidentification for the signal. r Q

Recapitulating, it may be seenthat the systemhereof is-disclosed toutilize both frequencydissection-and sampling dissection todevelop-numerical'values .which are then encoded to more concisedig-ital forms based upon relative significance. The resulting digitalcodes then afford concise digital identification of a sequence of ananalog signal.

Although the above analytical explanation was based on a frequencydissectionof the analog signal into three separate signals, it isreadily apparent that various numv bers of frequency bands may beemployed, depending upon the degree to which a signal is to be defined.Somewhat similarly, sampling rates and coding formats may vary withinwide limits depending upon the peculiar demands imposed upon aparticularsystem.

A system for dissecting an analog signal somewhat as considered'abovewith reference to FIG. 3 is shown in FIG. 4 and will now be consideredin detail. The analog signal is applied to a terminal 36 which isconnected to the input of a multiple band-pass frequency filter 38.

Various forms of filter-devices may be employed as the filter 38 toprovide three distinct signals in conductors 40, 42 and 44 respectively,which manifest three selecttuned circuits which have transformer-coupledoutupon receipt of a clock pulse to briefly pass the instant analogsignal amplitude received from the filter 38.

The analog values provided from the sampling circuits 46, 48 and 50 areapplied to accumulators 56, 58 and 60 respectively. These structures maysimply comprise analog registers, as well known in the prior art, someof which accumulate a potential as a capacitive charge to manifest anaccumulated analog value. Of course, various forms of analogaccumulators are well known in the art.

The accumulators 56, 58 and 60 are connected respectively to gatecircuits 66, 68 and 70 which also each receive a qualifying signal froma counter 72 that is driven by the output from the clock circuit 52.When the counter 72 reaches capacity, the next pulse received therebycauses an overflow from the counter, which qualifies the gates 66, 68and 70 resulting in the application of the contents of the accumulators56, 58 and 60 to a digital coding unit 74.

As will be described in detail below, the digital coding unit 74 (hereexemplified in a single form) provides binary-value signals through agate 76 to a register 78 which are developed to represent a value inaccordance with the relative magnitudes of the signals received from thegates 66, 68 and 70. The binary code value thus identifies an intervalof the analog signal which is received at the terminal 36 from whichsuch value was developed.

Assume now, for example, that'an operating interval of the system isdefined to be two seconds, and that at the conclusion of each suchtwo-second interval, the system provides a representative binary numberto the register 78. Assume further, as indicated above, that the analogsignal applied at the terminal 36 is dissected to provide threecomponent-frequency signals which are sampled at the rate of 100 samplesper second. Accordingly, the clock 52 provides pulses at l/lOOth of asecond and the counter 72 has a capacity to tally the clock pulses to'acount of 200, so that the counter overlfows every two seconds.

Assume still further as an operating aspect, that the filter 38 providesfequency component signals as follows: (1) output to conductor 40: 500cycles; (2) output to conductor 42: l,()()() cycles; and (3) output toconductor 44: 2,000 cycles. Accordingly, every 100th of a second, ananalog value is supplied from each of the sampling circuits 46, 48 and50 to be added to the contents of an associated one of the accumulators56, 58 and 60 respectively. Additionally, after each two second intervalof accumulation, the contents of the accumulators 56, 58 and 60 aregated in the form of signals Z1, Z2, and 23, through gates 66, 68 and 70respectively to the digital coding unit 74. At the instant concluding atwo-second interval, the digital coding unit 74 receives the overflowsignal from the counter 72 commanding a test operation whereby the orderof significance of the signals 21, E2, and Z3 is determined as a uniquesituation to provide code values that are supplied from the digitalcoding unit 74 through the gate 76 to the register 78. A very briefinterval after the digital coding unit 74 is actuated by the overflowpulse (applied at a test" input) the unit is reset or cleared by receiptof a pulse at a clear" input which pulse is received from the counter 72through a delay circuit The digital code developed by the coding unit 74may follow any ofa great many different formats depending upon specificapplication requirements and design. For example, the digital-valuesignals may be derived on the basis of the relative significance of thevalues accumulated in the accumulators 56, 58 and 60, somewhat asdescribed hereinafter. Alternatively, various other coding formats canbe employed as will be apparent to those skilled in the art. V

A fragment of one form of digital coding unit 74 is disclosed in detailin FIG. 5. As shown, the signals 2 l and Z 2 are applied to a comparator80 (in a Z 1 2 2" signal source 81) which comparator may take the formof an analog subtractor. In the event that the signal Z1 execces thevalue of the signal 22, an output is provided from the comparator to anand" gate 82 which is qualified by the test signal and which sets a flipflop 84 indicating relative magnitudes of the two signal-representedvalues. As a consequence, a binary signal 21 E 2 (descriptivelydesignated) from the flip flop 84 becomes high and the negation thereofbecomes low. The binary signal 22 Z3 (descriptively designated) may bedeveloped by a source 87 similar to the source 81.

The signals 21 Z2 and 22 E3" along with similar signals may then beapplied to logic and gates as well known in the art to develop digitalsignal codes according to a selected format as described in greaterdetail below.

Recapitulating, the system of FIG, 4 receives an analog signal and aftera predetermined test interval (two seconds) provides a binary valuerepresentative of the signal during the two-second interval.Consequently, a series or sequential set of such binary numbers may beeffectively employed to recognize a specific analog signal. That is,having once analyzed a particular pattern of an analog signal as from anaudio recording, representative digital signals may be developed forcomparison with a continuous analog signal (which may embody therecording) in search ofa coincidence to indicate similarity.

In a specific exemplary application hereof, as suggested above, abroadcast radio station might be monitored to obtain a continualcompilation of digital representations including those for musicalselections, i.e., recordings broadcast from thestation. Of course, toselectively determine the presence of digital representations indicativeof a recording and to identify each speciflc recording it is necessaryto construct a catalog or library of digital representations thatidentify the recordings of concern. Accordingly, such recordings areanalyzed in advance and representative sets of digital values aredeveloped which identify each recording. In view of the fact that thesignal under observation, as from a radio broadcasting station, is nottime synchronized, it is necessary to develop several thousand sets ofnumerical sequences (indicative of a recording) which are time-displacedin overlapped relationship. For example, the observed set of digitalvalues for a specific recording (musical selection) may vary with thetime relationship of the encoding system to the record signal,Accordingly, a plurality of time displaced sets of digital values aredeveloped so that coincidence with any one of the plurality during amonitoring operation indicates that the recording in question iscontained in the observed signal. Of course, varying standards ofidentify and deviation may be employed de pending upon the nature of thesystem.

In an exemplary form hereof, an identification fora recording mayconsist of ten digital values (derived from ten two-second intervals).ln such a format, the catalog'of template identifications for each ofthe recordings may be forty sets of digital values. For example,'assumethat analysis and encoding of an analog siga second identification.Thus, in an exemplary form,

hereof, some 40 seconds of analog signal is employed to produce 20 setsof digital valueswhic'h areoffset by /2 o e ondaad h,., .w.hi,qh incudes 29 seconds of the analog signal. The format of this operation isillustrated diagrammatically in FIG. 6. At the timen t t a .29. $999.1 nsrya pfplav s initiatedfrom which one set of digital values aredeveloped..At time 12 (one 25th of a second after [1) another twentysec- I 0nd time interval is initiated during which another set ofdigital values is developedrAccordingly, twenty sets (No. 1 through No.of digital'values are developed for comparison with the continuous flowof digital identifications that are developed from the monitoredsignalduring its observation. Upon a coincidence, or near coincidence, ofany'set with a sequence from the monitored signal (as provided by thestructure as depicted in FIG. 4) a recording is identified.

Recapitulating, a system as disclosed in FIG. 4 is first used to obtainseveral thousand sets of-catalog d-igital values which are developedfrom time-displaced portions of an analog signal as may be provided froma musical recording. Thereafter, a continuous analog signal (includingthe signal forms of the musical recordings) is monitored to provide asequence of digital values, using a system as shown in FIG. 4. Thecatalog values and the analog signal values are then compared in a dataprocessing operation to detect the appearance of specific recordings inthe analog signal. Thus, a radio broadcasting station can be monitored(internally or externally) to provide a tabulation of thespecificrecordingswhich are broadcast, without the necessity oflaborious andoften inaccuratemanual monitoring pro- I cedures.

As described above, the system is substantially analog in form. However,it may be advantageous to provide the system in a form which is moreextensively digital in nature. Such a system is shown in FIG. 7 and willnow be considered in detail to set forth another embodiment hereof as abasis for the claims. .Again, the system is disclosed to include asampling unit for dissecting an analog input. Specifically, the receivedaudio or other analog signal is supplied through a conductor 102 to asignal sampling unit 104 which is synchronized by pulses'that arereceived from a clock generator 106. Of course, the sampling rate mayvary widely and in accordance with current technical capabilities,however, sampling rates of 200 per second are reasonable in a presentembodiment of the system. The sampled signals (defining the input analogsignal) are supplied from the sampling unit 104 to an analogto-digitalconverter 108 that is also synchronized by the signal from, the clockgenerator 106. Various forms of such converters are well known in theprior art which are capable of supplying digitizedrepresentations ofanalog'samples at a predetermined sampling rate;

The digital representations (series 'or'parallel) from the convertcrl08are supplied through 'acablc 110 to a multiple band passdigitalfiltcr 112. The digitalfilter 112 provides four outputs, (l),'(2), (3)--and (4),each of which is a s'etof signal represented digital values for fourspecific frequency bandsof the'analog signal received through the cable110. That is,"th'e digital filter 112 is a digital equivalent of' thewell-known analog,

.- multiple=band-pa'ss filter apparatus. A form of, digital filtersuitable for use herein is disclosed in a publication entitled AnApproach to the Implementation of Digital Filters, by Jackson, Kaiserand McDonald; publishedin IEEE Transactions on Audio andElectroacoustics; Volume AU-l 6, "Number 3, September 1968. i

The four sets of digital signals 1), (2) (3) and (4) from the digitalfilter l 12 each consist of a series of digital values definitive of theamplitude" of one frequency component of the original analog-signalunder investigation. The signals (1),'(-2), (3) and(4) are applied re-.

'spectively, to digital accumulatorsul14, 1 15,}.116 and 117. Thesignals, as accepted by the accumulators, are representative ofabsolutevalues. That is, the sign digit of the signal or value represented isdropped. This con sideration is related to the rectification ofcomponent signals in the analog form ofthe presentinvention.

The accumulators 114, .115, 116 and 117 may take .a variety of differentforms, normally iricl udinga digital adder and a registerinterconnectedaswell known in the prior art. In addition to the digitalsignals, the accumulators each receive a binary fclear"- signal from acounter 120 which is connected to-b'e driven by pul'ses from the clockgenerator 106;If, for examp'le,theclock generator operates at a rate of200 pulses per second, the counter 1 20 may have a capability to countto 400 so as to provide the accumulations of a two second accumulationinterval. I

when the capacity of the counter 120 is exceeded, an overflow pulseisprovidedto clear the; accumulators ll4,' 115 116 and. 117, andsimultaneously transfer their contents through aset of gang;and, gates124, 125, 126 and 127 respectively to a group of comparatorjcircuits130,141, 142, 144, 146 and 148. The gang and" gates may each consist ofseveral individual and gates as well known in the prior art, associatedwith the individual conductors in the cables carrying the output signalsfrom the accumulators 114, 115, 116

and 1 17. I v e The signals that represent the digital values which arepassed through the gang gates 124 and are applied to a comparator 130which (as the other comparators) has two binary outputs. If thesummation'ofthe compo nent value represented by the signal (l),.i.e.,2(1), exceeds the value indicated by the summation of the signals (2),i.e., E (2), a high signal will appear in the conductor 132. In theevent that'the inverse is true, a high signal appears in the conductor134. This format is provided by each of the comparator circuits of FIG.7, including comparator circuits 141, 142, 144' and 146 and 148.

The comparator circuits may comprise a form of binary subtractors aswell known in theprior art, coupled to a flip flop circuit substantiallyas disclosed in FIG. 5. In the event for example, that thesignal-represented subtraction of the valueE(2) from the value E (1)results in a positive difference, a high level binary signal is receivedby the conductor 132. Conversely if the subtractive operation results ina negative value, the conductor 134 receives a high binary signal, Theoperation of the comparators 141, 142, 144, 146 and 148 is similar withthe result that twelve binary inputs C1 through C12 are developed whichare indicative of the relative magnitudes of the summation quantitiesprovided from the accumulators 114, 115, 116 and 117, to a decodingmatrix 150. The function of the decoding matrix is to perform logicaloperations to develop five-bit binary code signals controlled by therelative magnitudes of each of the summed quantities. Specifically, therelationship of the summed quantities to the logic combination ofsignals Cl through C12 and the resulting output codes are set forth inthe following chart:

From the above chart, it is apparent that a series of binary signalsrepresentative of five-bit binary numbers are developed at the output ofthe decoding matrix 150 which values are indicative of an interval ofobservation of the analog signal. As in the embodiment consid eredabove, the interval may consist of two seconds or may be varied toaccommodate other objectives. The structural details of the decodingmatrix 150 are explicit from the above chart in that the matrix simplyincorporates elements to accomplish the specific logic comparison, i.e.,and combinations.

The sets of binary signals developed from an interval of the analogsignal may be recorded as described above with reference to FIG. 4 andemployed as a part of a template catalog for comparison with a minotoredsignal as described with reference to FIG. 1. That is, having obtained adigital representation resulting from the dissection of an analog signalfor an interval, such digital representations may be variously employedas to identify portions of an analog signal under observation.

In some instances of operating a system in accordance herewith, thesummation values may be too close to each other to draw a significantdistinction. In such a situation, one of the comparators 130, 141, 142,144, 146 or 148 will provide no output which results in the occurrenceof a low signal at an output terminal 152 from the matrix 150. Ineffect, the signal appearing at the output 152 comprises simply an andcombination of the outputs from each of the comparators.

In the event of an ambiguity, it may be desirable to develop otherdigital values or alternatively to simply record the output from thecomparators 130, 141, 142, 144, 146 and 148. For example, in the eventof an ambiguity, the outputs from the comparators may comprise thebinary digits of a value in combination with the signal appearing at theterminal 152. Of course, a wide variety of different encoding schemesare readily useable with the system. However, the singificantconsideration lies in the appreciation that the encoding operationstemming from relative magnitudes of accumulated values accomplishes asubstantial reduction in the data yet preserves an identifyingconsideration. Although the above explanation has assumed a simplyone-to-one comparative relationship, it is also apparent that otherrelationships may be developed for increased flexibility of the system.Specifically, for example, such relationships might query whether or notthe summation of one of the values is more than twice the summation ofanother value. Thus, a great number of relationships are possible toformulate the basis for encoding the summation signals into a moreconcise digital code.

What is claimed is: 1. A system for statistical identification of atimereferenced substantially-continuous signal sequence, comprising:

timing means for defining a plurality of periods in time offset lappedrelationship and within an interval of said signal sequence;

means for analyzing said signal sequence during each of said periodsdefined by said timing means, to provide a plurality of representativedigital code signals; and

means for registering said plurality of representative digital codesignals as a statistical identification of said signal sequence. 1 l

2. A system according to claim 1 wherein said means for analyzing saidsignal sequence includes a digital filter means for providing digitalvalues from said signal sequence.

3. A system according to claim 1 wherein said means for analyzingincludes means for comparing represented magnitudes of components ofsaid signal sequence to provide representative binary signals.

4. A system according to claim 1 further including means for comparingsaid plurality of representative digital code signals from said meansfor registering with another plurality of representative digital codesignals.

5. A system according to claim 1 wherein said means for analyzing saidsignal sequence includes a digital filter means for providing digitalvalues from said signal sequence and wherein said means for analyzingincludes means for comparing represented magnitudes of components ofsaid signal sequence to provide representative binary signals.

6. A system according to claim 5 further including means for comparingsaid plurality of representative digital code signals from said meansfor registering with another plurality of representative digital codesignals to identify said signal sequence.

7. A system according to claim 1 wherein said means for analyzingfurther includes means for manifesting an ambiguity in said digital codesignals.

1. A system for statistical identification of a time-referencedsubstantially-continuous signal sequence, comprising: timing means fordefining a plurality of periods in time offset lapped relationship andwithin an interval of said signal sequence; means for analyzing saidsignal sequence during each of said periods defined by said timingmeans, to provide a plurality of representative digital code signals;and means for registering said plurality of representative digital codesignals as a statistical identification of said signal sequence.
 2. Asystem according to claim 1 wherein said means for analyzing said signalsequence includes a digital filter means for providing digital valuesfrom said signal sequence.
 3. A system according to claim 1 wherein saidmeans for analyzing includes means for comparing represented magnitudesof components of said signal sequence to provide representative binarysignals.
 4. A system according to claim 1 further including means forcomparing said plurality of representative digital code signals fromsaid means for registering with another plurality of representativedigital code signals.
 5. A system according to claim 1 wherein saidmeans for analyzing said signal sequence includes a digital filter meansfor providing digital values from said signal sequence and wherein saidmeans for analyzing includes means for comparing represented magnitudesof components of said signal sequence to provide representative binarysignals.
 6. A system according to claim 5 further including means forcomparing said plurality of representative digital code signals fromsaid means for registering with another plurality of representativedigital code signals to identify said signal sequence.
 7. A systemaccording to claim 1 wherein said means for analyzing further includesmeans for manifesting an ambiguity in said digital code signals.